Timing mechanism for printing apparatus employing flying printing action

ABSTRACT

A timing mechanism for printing apparatus utilizing a uniformly rotating type carrier provided with type characters arranged on the circumference thereof, against which a recording carrier is struck at a selected time by an impact element to effect the desired printing. For the determination of operating time points of control elements of the mechanism in sequence with the phase position of means which determines the time point of printing impact and thus corresponds to a time raster. The time raster comprises a means for scanning the phase position of the respective individual divisions of such time raster and a means is provided for scanning the phase position of a predetermined starting position of the type carrier. The means for forming the mechanical time raster is mounted on a shaft spaced from the type carrier shaft and carrying an additional rotatable timing member having a number of timing positions corresponding to the smallest whole number of revolutions of the type carrier including a whole number of revolutions of such rotatable timing member. Means revolving at the same angular velocity as the type carrier is cooperable with said rotatable timing member and permits the evaluation exclusively of one timing position thereof, corresponding with the starting point of the timing member during a revolution of the type carrier, and generates a synchronizing pulse.

United States Patent Kling [54] TIMING MECHANISM FOR PRINTING APPARATUS EMPLOYING FLYING PRINTING ACTION [72] Inventor: Adam Kling, Munich, Germany [73] Assignee: Siemens Aktiengesellschaft, Berlin and Munich, Germany [22] Filed: Dec. 12, 1969 [21] Appl. No.: 884,589

[30] Foreign Application Priority Data Dec. 20, 1968 Germany ..P 18 16 076.4

[52] US. Cl. ..101/93 C, 197/49, 178/34 [51] Int. Cl. ..B41j 23/34 [58] Field of Search ..101/93 C; 178/34; 197/49 [56] References Cited UNITED STATES PATENTS 3,442,364 5/1969 Ragen ..101/93 C X 2,906,200 9/1959 Pfleger ..101/93 C 2,831,424 4/1958 MacDonald ..101/93 3,007,399 11/1961 Sasaki et a1. ..10l/93 C 3,117,514 1/1964 Doersam ..l01/93C 3,420,166 1/1969 Ellis et al7 ..lOl/93 C 3,420,164 1/1969 Lee ..101/93 C 2,936,704 5/1960 l-lense ..10l/93 C 3,001,469 9/1961 Davis et al. ..101/93 C 3,332,068 7/1967 McLaughlin etal ..101/93 CX 3,363,238 1/1968 Clark et al ..101/93 C X [451 Aug. 29, 1972 Primary Examiner-Robert E. Pulfrey Assistant Examiner-R. T. Rader Attorney-Hill, Sherman, Meroni, Gross & Simpson [57] ABSTRACT A timing mechanism for printing apparatus utilizing a uniformly rotating type carrier provided with type characters. arranged on the circumference thereof, against which a recording carrier is struck at a selected time by an impact element to effect the desired printing. For the determination of operating time points of control elements of the mechanism in sequence with the phase position of means which determines the time point of printing impact and thus corresponds to a time raster. The time raster comprises a means for scanning the phase position of the respective individual divisions of such time raster and a means is provided for scanning the phase position of a predetermined starting position of the type carrier. The means for forming the mechanical time raster is mounted on a shaft spaced from the type carn'er shaft and carrying an additional rotatable timing member having a number of timing positions corresponding to the smallest whole number of revolutions of the type carrier including a whole number of revolutions of such rotatable timing member. Means revolving at the same angular velocity as the type carrier is cooperable with said rotatable timing member and permits the evaluation exclusively of one timing position thereof, corresponding with the starting point of the timing member during a revolution of the type carrier, and generates a synchronizing pulse.

6 Claims, 4 Drawing Figures 1 3|, ELECTRONIC COUNTING cmcun PATENTEU M1929 I972 SHEET 1 [IF 2 IIQIIII ATTY 211 3.,

PATENTEDAUBZQ m2 131687.071

SHEET 2 BF 2 TIMING MECHANISM FOR PRINTING APPARATUS EMPLOYING FLYING PRINTING AQTION BACKGROUND OF THE INVENTION The invention relates to printing apparatus utilizing a flying type action in which a uniformly rotating type carrier, having the type characters arranged on the circumference thereof, is adapted to imprint a desired character on a recording carrier which is moved through a printing station at which it is imprinted by the action of an impact element operable at a selected time point when the desired character on the type carrier is in a printing position. More particularly, the invention is directed to a mechanism for determining the timing points of control elements of the printing apparatus dependent upon the phase position of means determining the time point of impact or printing for the respective characters, and thus functioning in the manner of a time raster, employing means or sensing the phase position of the timing raster divisions of such means, and also employing means sensing the phase position of a pre-selected starting position of the type carrier.

The use of mechanical means functioning in the manner of a time raster, hereinafter referred to as a mechanical time raster, for example, an impact producing drive wheel is known, particularly with respect to printing mechanisms employed in high speed printers, for example, those employing a flying type printing action. Printing apparatus of this type in which the printing or impact time points are determined by such a mechanical time raster, are so constructed that each typographic image or character conducted past the printing station has allocated thereto in phase, a raster point or division of a corresponding uniformly moving mechanical time raster. The printing operation is effected by means of a suitable intermediate member, normally termed a coupling member," whereby there is briefly established a connection between the means representing a corresponding raster time point and the printing or impacting hammer. It will be apparent that for the production of the coupling between an element representing a particular rasterpoint of the mechanical time raster and the printing hammer by means of the coupling member, there is available, as a result of the phase allocation of the movement of the raster point and the character of the type carrier, merely the time interval between two successively following raster elements representing points. Obviously, as the printing speed is increased there results a corresponding shortening of the time interval available for the coupling process. Consequently, it is necessary to endeavor to utilize such time interval as fully as possible and to exclude sources of error as well as increase precision in the determination of the operating time point for the coupling between the elements representing raster points and the printing hammer by means of the actuation of the coupling member.

It will be appreciated that as there exists a time delay between the operation of the printing hammer and the selection of a printing time point proper, the mechanical time raster must rotate phase-shifted with respect to the rotating type carrier. The time span required for the operation of the coupling member, however, is dependent exclusively on the angular position of the elements of the mechanical time raster with respect to the' actuating position of the coupling member.

Obviously, these factors must be considered for the optimum utilization of the time period available for the coupling process. For the actual printing operation, there is necessary the actual selection of a desired one of the successively following coupling possibilities, i.e., the selection of the coupling function at a time to effect the printing of a desired character upon the recording carrier. For the determination of this time point, electronic switching arrangements are employed which determine the desired time point at which the triggering device for the coupling member is actuated to effeet a printing onto the recording carrier of the selected type character.

To accomplish these results, it is necessary to supply to the electronic circuit arrangement, for example, an electronic counting chain, the particular phase position of the type carrier. Accordingly, as for each symbol or character to be printed, a counting pulse is supplied to the electronic circuit, for each such symbol there is arranged on the mechanical time raster a corresponding time point, and as the position of such raster point is already scanned, for the reason above mentioned, it is expedient to use the timing pulses obtained in the scanning of the position of the time raster point as counting pulses for the electronic circuit arrangement.

Such an electronic counting chainwould employ as many counting places as the number of characters carried by the type carrier. It will be appreciated, for example, as a result of erroneous pulses, or, in particular, following a discontinuance of operation of the device, there can occur a functional displacement between the type carrier and the electronic counting chain, as a result of which it is necessary, to avoid false printing, to derive a further counting pulse from the type carrier which represents a predetermined starting position of the latter and thereby assure the actuation of the electronic counting chain in the desired time relation. However, in order to assure a functionally correct operation of the entire system, it is necessary to effect an agreement of such synchronizing pulse with a predetermined symbol timing pulse derived from the mechanical time raster.

In known arrangements, the devices employed for sensing these two criteria are individually adjustable, as a result of which a shifting of a scanning device which scans the character or symbol timing pulses in the phase positions of the mechanical time raster necessitates in such known mechanisms a corresponding readjustment of the scanning means from which the synchronizing pulses from the type carrier are derived.

The present invention therefor is directed to the production of a device by means of which is possible, through the timing adjustment of the counting pulses derived in the phase positions of the time raster, to achieve a simultaneous timing adjustment of the synchronizing pulses determined by the position of the type carrier, and in particular, independently of whether the type carrier rotates synchronizingly with the mechanical time raster or merely in phase therewith, i.e., with a certain rotative speed translation or reduction.

SUMMARY OF THE INVENTION The invention is directed to printing apparatus employing flying printing action and in particular to a mechanism for determining the operative timing points of control elements in which, in addition to a timing element or wheel which represents a mechanical time raster and which defines the individual raster timing points, there is arranged for rotation therewith, as for example mounted on the same shaft, an additional timing member or wheel having a number of timing positions which corresponds to the smallest whole number of revolutions of the type carrier for a corresponding whole number of revolutions of the timing wheel, which additional timing member is cooperable with means which enables an evaluation of only one timing position of such additional timing member during a revolution of the type carrier, whereby a synchronizing pulse may be accurately generated.

More particularly, in accordance with the invention the timing generator for the symbol or character timing and the timing generator for the synchronizing pulses may be disposed on a common shaft, such as the shaft carrying the means forming the mechanical time raster.

, As a reduction ratio is usually employed between the rotating speeds of the type carrier and the mechanical time raster means, the timing member or wheel of the timing generator for the synchronizing pulses will in most cases contain several timing points for the determination of the synchronizing impulses, more specifically as many as the number of full revolutions of the type carrier taking place in a whole number of revolutions of the mechanical time raster means. As a result it is necessary to provide means for effecting a preselection of the timing point of the timing wheel which is to determine the synchronizing pulse for a particular revolution of the type carrier. The respective means for the determination of the time raster and of the synchronizing pulse, along with the respective sensing devices can be disposed immediately adjacent to one another and can be aligned with respect to one another and adjusted in a very simple manner.

In accordance with the preferred form of construction according to thy invention, the sensing devices for the individual symbol timing points of the time raster and the devices scanning the synchronizing pulse points of the additional timing wheel may be constructed as a unitary structure which is pivotally adjustable about the axis of the tinting wheels.

It will be appreciated that by a pivotal movement of the sensing device for the individual timing points of the time raster compensation may be effected for the mechanical delay or lag taking place between the time of initial actuation of the coupling member and the actual impact of the type hammer on the recording media, and simultaneously therewith there is effected a corresponding adjustment of the device sensing the synchronization timing points. Such an adjustment, for example, may become necessary after a large number of hours of operation, as a result of which the response time of the control elements may undergo changes. A correction thereof, accordingly is possible without requiring any substantial technical knowledge and without any special difficult adjustment techniques.

In accordance, with a further development of the invention, inductive scanning heads are employed for scanning or sensing the individual timing points as well as the synchronizing pulse points of the timing wheel for determining the starting position of the type carrier. In this connection, it is advantageous to arrange the inductive scanning heads so that they are adjustable in the direction of motion of the means representing the individual timing points. The use of inductive scanning heads represents a relatively simple arrangement having maximum functional reliability for transforming the individual timing points and the synchronizing pulse points of the respective timing members into electrical pulses utilizable by the electronic circuit arrangement for the actuation of the printing apparatus.

In accordance with another development of the in vention, there are utilized, in place of inductive scanning means, respective light-responsive systems for effecting the scanning of the individual timing points as well as the synchronizing pulse points. In this embodiment of the invention, there is provided on the shaft carrying the mechanical time raster means a disc having slits in at the corresponding timing points which is cooperable with a disc rotatable with the type carrier, and having the same angular velocity, which is provided with a recess or opening adapted to expose the proper timing slits to a common light-responsive system whereby only a single scanning means, Le, a single light-responsive system may be employed for the generation of the synchronizing pulse.

Preferably, the individual time raster elements of the mechanical time raster are utilized in the connection with the scanning means to generate the individual timing pulses whereby such individual time raster elements generate the timing signal which effect the actuation of the coupling member with the printing hammer.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings wherein like reference characters indicate like or corresponding parts:

FIG. 1 is a perspective view of a simplified printing apparatus, with portions thereof broken away to show details thereof, employing inductive scanning devices for the generation of the individual timing pulses and the synchronizing pulses;

FIG. 1a is a fragmentary detail view, illustrating a timing wheel and the impact wheels in side elevation;

FIG. 2, illustrates a portion of a printing apparatus such as illustrated in FIG. I but utilizing light-responsive systems as the scanning means for effecting generation of the respective individual timing pulses and the synchronizing pulses; and

FIG. 3 is a transverse section through the structure illustrated in FIG. 2 illustrating details of the rotating members employed with the light-responsive system for deriving the synchronizing pulses.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings and more particularly to FIG. 1 thereof, the reference 1 designates an electric motor which is operative through a gear train comprising gears 2, 3 and 4 to drive a disc-shaped type carrier 5 at a constant speed. The respective type symbols or characters are arranged on the circumference of the type carrier and are thus adapted to be successively conducted past the printing station, designated generally by the letter S, at which an imprint on the recording carrier 6 is to be effected, all of such characters on the types carrier being adapted to pass the printing station at least once within the duration of one printing cycle. Rigidly connected to and rotatable with the gear 3 is an impact-initiating arrangement comprising two impact wheels 7 and 8 whereby such impact wheels rotate in phase with the type carrier 5.

As will be apparent from the reference to FIG. 1, the teeth on the one impact wheel 7 are offset a half tooth division with respect to the teeth on the other impact wheel 8, and disposed adjacent to the path of the teeth on the respective impact wheels are respective coupling members 11 and 12, the free ends of which are substantially aligned with the teeth on corresponding impact wheels. The respective coupling members 11 and 12 are adapted to be controlled by respective electromagnets 9 and 10, actuation of either one of which is operative to actuate a corresponding armature operatively connected with an adjacent end of a corresponding coupling member whereby upon energization of one of the electromagnets, the associated coupling member will be longitudinally moved to dispose the adjacent end thereof between two teeth on the associated impact wheel, whereby the next following tooth thereon, in the direction of movement of the latter, will engage such end of the coupling member, moving it in the direction of rotation of such impact wheel. Such movement of the actuated coupling member is transmitted to the free end of a pivoted lever 13 which carries at its opposite free end a printing hammer disposed at the printing station S whereby it may strike the lower face of the record medium 6 causing the upper face thereof to strike the type carrier 5, thereby forming an imprint of the character positioned at the station S at such an instant. The lever 13 is adapted to be restored to its original position by the action of a spring 14.

It will be appreciated that through the use of two impact wheels 7 and 8 in place of a single wheel the required impact teeth are distributed in alternating arrangement on the respective wheels 7 and 8 whereby the time available is correspondingly increased for the engaging movement of the coupling members 11 and 12 into position for coupling a corresponding impact tooth of the selected wheel with the lever carrying the printing hammer. The number of impact teeth on the two impact wheels is so selected, taking into consideration the transmission ratio between the impact wheel mechanism and the type carrier 5 and the phase position with respect to the type carrier, that the recording carrier 6 can be struck by the printing hammer, through actuation by the lever 13, only at a point of time at which a character on the type carrier 5 is disposed opposite the printing hammer. It will be apparent that in order to print a specific character disposed on the type carrier 5, it is necessary to energize one of the electromagnets 9 or at a specific time point which is determined by the phase. position of the type character on the type carrier and thus by the phase relationship thereof with respect to the mechanical time raster, corresponding to the phase position of the type carrier. For the determination of this phase position there are provided, in the construction of FIG. 1, respective inductive heads 15, 16 and 17, the head being disposed to sense or scan the teeth moving past the same of the two impact wheels 7 and 8 and being connected to an electronic counting chain 31 to thereby count the type characters on the type carrier 5 conducted past the printing station in the same time period. The initial or staring position of the type carrier as well as the starting position may be determined through 31 electronic counting chain. The pulses supplied may determine the starting point through the cooperation of the other two inductive scanning heads 16 and 17 Assuming a transmission ratio of the speeds between the type carrier 5 and the impact wheels 7, 8 is as previously mentioned, is assumed to be 3:2, after each 2/3 revolution of the impact wheels 7, 8 which corresponds to one complete revolution of the type carrier 5, a pulse must be produced when the cooperation of the scanning heads 16 and 17 and an AND gate 30. To accomplish this result, there is disposed on the shaft carrying the impact wheels 7, 8 in position for coaction with the scanning head 16, a timing member 18 which is provided with three timing points cooperable with such scanning head, such timing points being offset by However, as the desired synchronizing pulse is required for each revolution of the type carrier 5, which corresponds to only 2/3 revolution, i.e., 240 of the impact wheels, provision must be made to permit utilization only of the desired synchronizing pulse derived from the scanning head 16. This is accomplished by the provision of a further timing member or wheel 19 having only a single'timing point which is so disposed with respect to the starting position of the type carrier 5 that a resulting pulse at the scanning head 17 will designate the starting position of the type tion of the type carrier. The scanner head 17-and cooperable element 19, including circuitry responsive thereto should be so designed that the pulse taken from the element 19 permits a half revolution of the type carrier 5, by utilizing the synchronous pulse generated by the member 18 the corresponding timing point of the member 18 which will be operable as a synchronizing pulse over a period preferably up to a half turn of the type carrier 5. In other words, the desired synchronizing signal will be designated as such and available for utilization even though it may be presented within one half revolution of the type carrier following the passage of the zero position thereof through the printing station. Obviously, this can readily be accomplished with known techniques. In the embodiment illustrated the two inductive scanning heads 15 and 16 are mounted on a common supporting yoke or bracket 20, which is pivotable about the axis of the shift carrying the wheels 7, 8, whereby the operating time point can be readily effected by merely suitably rotating the bracket 20, which obviously can be efficiently accomplished without the use of highly trained technicians.

The overall operation of the structure illustrated in FIG. 1, assuming that each printing cycle corresponds to one revolution of the type carrier 5 and that the respective elements of the structure are in the position as illustrated in FIG. 1. The type carrier is disposed with the starting position thereof at the printing station S, the timing point of the member 19 disposed to energize the scanning head 17 and the scanning heads and 16 adapted to be energized by the adjacent individual timing points of the impact wheel 8 and of the timing member 18 respectively. At the same time the impact hammer carried by the lever 13 is in its lowermost position out of operative engagement with the record 6 while both of the coupling members 11 and 12 are disposed with their adjacent free ends out of the path of the wheels 7 and 8, as both of the electromagnets 9 and 10 are deenergized. In this connection it temporarily will be assumed that no delay or lag exists between energization of one of the electromagnets 9,10 and impact of a type hammer on the recording media. As previously mentioned, the arrangement illustrated is adapted to be utilized with suitable counting means as for example, electronic counting chain 31 in which an initiation of the count is effected by the proper synchronizing pulse from the head 16. In the present operation for example, the passage of the timing point of the member 19 by the scanning head 17 will result in the production of a pulse which is adapted to permit the simultaneously occurring pulse from the scanning head 16 to initiate actuation of such counting chain, which will then count the number of individual teeth on the impact wheels 7, 8 operatively passing the scanning head 15. When the count has reached that representing a selected type character on the type carrier 5 the appropriate electromagnet 9, 10 will be energized with the resulting movement of its armature being operative to thrust the free end of the corresponding coupling member 11, 12 between two teeth on the corresponding impact wheel 7, 8 whereby the next following tooth will be operatively coupled, by the actuated coupling member, to the adjacent end of the lever 13 to move the latter downwardly and thus move the type hammer at the opposite end of the lever upwardly into impacting engagement with the record carrier 6 and impacting the latter on the type carrier 5, a suitable ribbon or tape being interposed therebetween to produce the desired imprint on the record medium.

However, obviously, a certain amount of delay will take place in the mechanical linkage between the electromagnets 9, 1t and the type hammer carried by the lever 13, in view of which, to assure actuation of the type hammer at the exact instant that the desired character is at the printing station, it is necessary to effect energization of the selected magnet at a time point prior to the actual positioning of the desired type character at the printing station and as previously mentioned this may be accomplished by pivoting the bracket and thus shifting the scanning heads 15 and 16 in a clockwise direction as viewed in FIG. 1 a sufiicient distance to exactly compensate for the time lag referred to. Likewise, as previously mentioned, as such compensating adjustment will result in the desired synchronizing pulse from the scanning head 16 not taking place exactly simultaneously with the pulse from the scanning head 17, the pulse derived from the scanning head 17 should be made operative, as a result of the construction and arrangement thereof, and/or the circuit associated therewith, that such pulse will be effective over the entire normal range of adjustment of bracket 20 and thus the head 15 and 16, whereby the synchronizing pulse from the head 16 will be operative to start the counting chain irrespective of the phase relation thereof with respect to the operation of the scanning head 17.

FIGS. 2 and 3 illustrate another embodiment of the invention which generally functions in a manner corresponding to that of FIG. 1 but which employs light responsive means for the generation of the individual and synchronizing pulses, as well as utilizing mechanical means for insuring selection of the proper synchronizing pulse for the start of the counting chain.

In this arrangement, two light-responsive systems are employed consisting of respective light sources 21, and 22 and corresponding photo-sensitive electric circuit elements 23 and 24 which are adapted to be supported on a common, pivotally movable bracket 25, adapted to be adjusted pivotally about the axis of the impact wheels 7, 8. As apparent from a reference to FIG. 2, the light source 21 and photo-sensitive element 23 are optically aligned whereby light from the source 21 can pass through aligned slits in the adjacent portions of the bracket 25 to the photosensitive cell 23, the light path, however, intersecting the path of the teeth on the impact wheels 7, 8.

In like manner, light from the source 22 may pass through respective slits in the corresponding portions of the bracket 25 to the photo-sensitive cell 24 when one of the timing slits 26 of a timing wheel 27, carried by the shaft supporting the impact wheel 7 and 8, is in proper alignment and simultaneously there with therecess 28 of the disc 29, mounted on the type carrier shaft, is likewise in alignment with the light path. Referring to FIG. 3, it will be apparent that the portions of the discs 27 and 29 are such that the peripheral portion of rotating disc 27 containing the slits 26 and the corresponding peripheral portion of the disc 29 adapted to intersect the path of the source 22 are proportioned to have the same angular velocities and thus are rotating in the ratio of 3:2. Consequently, the recess 28 will be optically aligned with the light path from the source 22 only when the proper slit 26 intersects such light path and will block such light path when any other slit than the proper one intersects such light path. it will be appreciated that the use of the disc 29 eliminates the necessity of a third scanning means, enabling the use of only two light-responsive systems.

It will be appreciated that the operation of the construction illustrated in FIGS. 2 and 3 is substantially identical with that of H6. 1 with the exception that the light-responsive cell 24 will provide a single synchronizing pulse which may be directly utilized for actuation of thy counting chain. Obviously the portions of the discs 27 and 29, as well as the recess 28 will be such as to permit a desired range of adjustment of the bracket 25, generally corresponding to the adjustment of the bracket 20 of FIG. 1.

Having thus described my invention, it will be obvious to those skilled in the art from the disclosure herein given that various immaterial modifications and changes may be made therein without departing from the spirit of my invention.

l claim as my invention:

1. in a timing mechanism for high speed printing apparatus including,

a uniformly rotating type carrier provided with type characters arranged along the circumference thereof and a printing station including a printing hammer disposed adjacent to the circumference of said type carrier,

a shaft carrying said type carrier,

a motor,

a gear train driving said shaft from said motor at a uniform rate of speed,

a parallel impact wheel drive shaft driven by said motor through said gear train at a fixed rate of speed and at a predetermined speed ratio with respect to the speed of said type carrier,

two impact wheels on said impact wheel drive shaft,

each of said impact wheels having teeth uniformly spaced thereabout each corresponding to a character on said type carrier and constituting a mechanical time raster,

the teeth on one impact wheel being offset a half tooth with respect to the teeth on the other impact wheel,

individual coupling members for each impact wheel insertible between the teeth of the associated impact wheel, for actuating said printing hammer,

individual electromagnetic means for each coupling member,

means actuated by said electromagnetic means for successively inserting said coupling members between the teeth of said impact wheels, to successively actuate said type hammer,

at least two cooperating scanning heads,

a first of said scanning heads scanning the teeth of said impact wheels,

an electronic counting chain connected between the first of said scanning heads and said electromagnetic means, for energizing said electromagnetic means to effect the successive actuation of said printing hammers,

a first timing member on said impact wheel drive shaft, having timing points determined by the speed ratio between said type carrier and said impact wheels,

said second scanning head cooperating with the timing member on said impact wheel drive shaft to generate synchronizing pulses for said electronic counting chain sensing the phase position of teeth of said impact wheels, and

a second timing member on said shaft carrying said type carrier and cooperable with said first timing member on said impact wheel drive shaft,

a third scanning head cooperable with said second timing member, and generating a pulse for said electronic counting chain sensing the starting position of the type carrier and cooperating with said first timing head to initiate and coordinate the successive energization of said electromagnetic means in accordance with rotation of said type carrier and the phase position of the starting point of rotation of said type carrier.

2. The timing mechanism for high speed printing apparatus of claim 1,

wherein the scanning heads are inductive scanning heads for generating cooperating timing pulses for each type point on the type carrier and for sensing the phase position of the impact wheels and initiating the printing operation at a predetermined starting position of the type carrier.

3. The timing mechanism for high speed printing apparatus of claim 2,

wherein the first and second mentioned scanning heads are mounted on a common bracket,

wherein the bracket is adjustably movable about the axis of the impact wheel drive shaft to vary the phase of operation of the first and second scanning heads relative to the phase of operation of the third mentioned scanning head and attain the energization of the electromagnetic means prior to the positioning of the selected type carrier at the printing station to compensate for the time lag between the energization of the electromagnetic means and the insertion of a selected coupling member between the teeth of an impact wheel.

4. In a timing mechanism for high speed printing apparatus including,

a uniformly rotating type carrier provided with type characters arranged along the circumference thereof and a printing station including a printing hammer disposed adjacent to the circumference of said type carrier,

a shaft carrying said type carrier,

a motor,

a gear train driving said shaft from said motor at a uniform rate of speed,

a parallel impact wheel drive shaft driven by said motor through said gear train at a fixed rate of speed, at a predetermined speed ratio with respect to the speed of said type carrier,

two impact wheels on said impact wheel drive shaft,

each having teeth uniformly spaced thereabout each corresponding to a character on said type carrier and constituting a mechanical time raster,

the teeth on one impact wheel being offset a half tooth with respect to the teeth on the other impact wheel,

individual coupling members for each impact wheel insertible between the teeth of the associated impact wheel, for actuating said printing hammer,

individual electromagnetic means for each coupling member, means actuated by said electromagnetic means for successively inserting said coupling members between the teeth of said impact wheels, to successively actuate said type hammer,

at least two cooperating scanning means,

a first of said scanning means comprising light-transmitting means on one side of said impact wheels projecting a ray of light between the teeth of said impact wheels and a light responsive means on the opposite side of said impact wheels in position to receive. the ray of light projected by said lighttransmitting means,

an electronic counting chain connected between said light responsive means and said electromagnetic means, for energizing said electromagnetic means to effect the successive actuation of said printing hammer in timed relation with respect to rotation of said type carrier,

a timing member on said impact wheel drive shaft having timing points determined by the speed ratio between said impact wheel drive shaft and said type carrier shaft,

a second timing member on said shaft carrying said type carrier,

and a second scanning head cooperating with said two timing members and including a light-transmitting member on one side of one of said timing members and a light responsive member on the opposite side of the opposite of said timing members,

said light responsive member receiving a beam of light when said first and second timing members are properly related with respect to each other,

recess therein proportioned in accordance with the speed ratio between said first and second timing member, said second disk blocking the passage of light through a slit in said first timing member except when the proper slit intersects the ray of light transmitted by said member.

6. The timing mechanism for a high speed printing apparatus of claim 5, including a single mounting bracket for each of said scanning means and mounted for adjustment about an axis coaxial with the axis of rotation of said impact wheel drive shaft, to start the counting chain to lag the energization of said electromagnetic means by an amount to take care of the lag between said electromagnetic means and actuation of the printing hammer.

light-transmitting 

1. In a timing mechanism for high speed printing apparatus including, a uniformly rotating type carrier provided with type characters arranged along the circumference thereof and a printing station including a printing hammer disposed adjacent to the circumference of said type carrier, a shaft carrying said type carrier, a motor, a gear train driving said shaft from said motor at a uniform rate of speed, a parallel impact wheel drive shaft driven by said motor through said gear train at a fixed rate of speed and at a predetermined speed ratio with respect to the speed of said type carrier, two impact wheels on said impact wheel drive shaft, each of said impact wheels having teeth uniformly spaced thereabout each corresponding to a character on said type carrier and constituting a mechanical time raster, the teeth on one impact wheel being offset a half tooth with respect to the teeth on the other impact wheel, individual coupling members for each impact wheel insertible between the teeth of the associated impact wheel, for actuating said printing hammer, individual electromagnetic means for each coupling member, means actuated by said electromagnetic means for successively inserting said coupling members between the teeth of said impact wheels, to successively actuate said type hammer, at least two cooperating scanning heads, a first of said scanning heads scanning the teeth of said impact wheels, an electronic counting chain connected between the first of said scanning heads and said electromagnetic means, for energizing said electromagnetic means to effect the successive actuation of said printing hammers, a first timing member on said impact wheel drive shaft, having timing points determined by the speed ratio between said type carrier and said impact wheels, said second scanning head cooperating with the timing member on said impact wheel drive shaft to generate synchronizing pulses for said electronic counting chain sensing the phase position of teeth of said impact wheels, and a second timing member on said shaft carrying said type carrier and cooperable with said first timing member on said impact wheel drive shaft, a third scanning head cooperable with said second timing member, and generating a pulse for said electronic counting chain sensing the starting position of the type carrier and cooperating with said first timing head to initiate and coordinate the successive energization of said electromagnetic means in accordance with rotation of said type carrier and the phase position of the starting point of rotation of said type carrier.
 2. The timing mechanism for high speed printing apparatus of claim 1, wherein the scanning heads are inductive scanning heads for generating cooperating timing pulses for each type point on the type carrier and for sensing the phase position of the impact wheels and iniTiating the printing operation at a predetermined starting position of the type carrier.
 3. The timing mechanism for high speed printing apparatus of claim 2, wherein the first and second mentioned scanning heads are mounted on a common bracket, wherein the bracket is adjustably movable about the axis of the impact wheel drive shaft to vary the phase of operation of the first and second scanning heads relative to the phase of operation of the third mentioned scanning head and attain the energization of the electromagnetic means prior to the positioning of the selected type carrier at the printing station to compensate for the time lag between the energization of the electromagnetic means and the insertion of a selected coupling member between the teeth of an impact wheel.
 4. In a timing mechanism for high speed printing apparatus including, a uniformly rotating type carrier provided with type characters arranged along the circumference thereof and a printing station including a printing hammer disposed adjacent to the circumference of said type carrier, a shaft carrying said type carrier, a motor, a gear train driving said shaft from said motor at a uniform rate of speed, a parallel impact wheel drive shaft driven by said motor through said gear train at a fixed rate of speed, at a predetermined speed ratio with respect to the speed of said type carrier, two impact wheels on said impact wheel drive shaft, each having teeth uniformly spaced thereabout each corresponding to a character on said type carrier and constituting a mechanical time raster, the teeth on one impact wheel being offset a half tooth with respect to the teeth on the other impact wheel, individual coupling members for each impact wheel insertible between the teeth of the associated impact wheel, for actuating said printing hammer, individual electromagnetic means for each coupling member, means actuated by said electromagnetic means for successively inserting said coupling members between the teeth of said impact wheels, to successively actuate said type hammer, at least two cooperating scanning means, a first of said scanning means comprising light-transmitting means on one side of said impact wheels projecting a ray of light between the teeth of said impact wheels and a light responsive means on the opposite side of said impact wheels in position to receive the ray of light projected by said light-transmitting means, an electronic counting chain connected between said light responsive means and said electromagnetic means, for energizing said electromagnetic means to effect the successive actuation of said printing hammer in timed relation with respect to rotation of said type carrier, a timing member on said impact wheel drive shaft having timing points determined by the speed ratio between said impact wheel drive shaft and said type carrier shaft, a second timing member on said shaft carrying said type carrier, and a second scanning head cooperating with said two timing members and including a light-transmitting member on one side of one of said timing members and a light responsive member on the opposite side of the opposite of said timing members, said light responsive member receiving a beam of light when said first and second timing members are properly related with respect to each other, and said second light responsive member providing a single synchronizing pulse which may be directly utilized for actuating the counting chain energizing said electromagnetic means.
 5. The timing mechanism for a high speed printing apparatus of claim 4, wherein the first timing member comprises a disk having a plurality of equally spaced slits therein, the second timing member comprises a disk having recess therein proportioned in accordance with the speed ratio between said first and second timing member, said second disk blocking the passage of light through a slit in said first timing member except when thE proper slit intersects the ray of light transmitted by said light-transmitting member.
 6. The timing mechanism for a high speed printing apparatus of claim 5, including a single mounting bracket for each of said scanning means and mounted for adjustment about an axis coaxial with the axis of rotation of said impact wheel drive shaft, to start the counting chain to lag the energization of said electromagnetic means by an amount to take care of the lag between said electromagnetic means and actuation of the printing hammer. 